The present invention relates to robotic systems for handling wafers in which an end effector is used to grip a wafer. More specifically, this invention relates to such systems wherein the end effector incorporates transporting and sensing capability for mapping wafers, automated calibrating of a robot to accurately position or move itself to carry out desired robotic operations, and the like.
Microelectronic devices (e.g., integrated circuits, flat panel displays, thin film heads for computer disk drives, micromechanical machine devices, and the like), often are produced from wafers of semiconductor material. During the course of manufacture, the wafers, which may bear one or more partially formed devices depending upon the stage of manufacture, are typically housed in wafer holding structures, or the like. Such holding structures typically include a plurality of closely spaced apart slots, for holding a wafer. Depending upon the kind of holding structure, batches of the wafers may be held in a particular orientation, including horizontally or vertically. Holding structures may be used to transfer one or more wafers between tools in a fabrication facility. Other kinds of holding structures may be used to transfer one or more wafers among locales within a tool or tool cluster. Still others may be used to hold wafers during a manufacturing procedure.
Various types of wafer handling devices are known for transporting wafers to and from wafer holding structures. Many use a robotic arm having a gripping member that can hold or otherwise grip a wafer. The gripping member often is referred to as an end effector. The end effector typically enters the holding structure through a narrow gap between a pair of adjacent wafers to retrieve or replace a wafer. The end effector generally is thin, rigid, and positionable with high accuracy to fit between the closely spaced apart wafers in a holding structure.
Wafers of semiconductor material are supplied in many sizes. Conventionally, wafers having a diameter of 200 millimeters (xe2x80x9cmmxe2x80x9d) have been used widely in the manufacture of microelectronic devices. More recently, semiconductor production systems have used 300 mm diameter wafers, with even larger diameter wafers under consideration as well. Regardless of the size, it may be desirable for a particular end effector to be able to hold wafers in different orientations, e.g., vertically as well as horizontally. For example, assignee""s copending U.S. Provisional Patent Application Serial No. 60/338,057 filed Nov. 13, 2001, for REDUCED FOOTPRINT TOOL WITH AUTOMATED PROCESSING OF MICROELECTRONIC SUBSTRATES, and bearing attorney docket no. FSI0080/P1, describes a low footprint tool in which a wafer transfer robot removes horizontal wafers from an industry standard front opening unified pod (xe2x80x9cFOUPxe2x80x9d), flips the wafers from a horizontal to a vertical orientation, and then stores them vertically in a holding structure for processing. It would be desirable to provide an improved end effector design that provides this transport capability.
In-process semiconductor wafers are quite valuable. It is not uncommon for an in-process semiconductor wafer bearing a plurality of partially formed devices to have a value that exceeds several hundred thousand dollars or more per wafer or batch. It is important, therefore, to handle such wafers carefully to avoid breaking or otherwise damaging them. One step in which in-process wafers are susceptible to damage is during transport to and from a wafer holder. To minimize the risk of damage during such transport, it is common in the industry to electrically, optically, and/or otherwise scan a holder with appropriate sensors to determine the presence and/or absence of wafers, correct orientation of wafers stored in the holder, location of wafers and/or open storage positions, and/or other characteristics of the holder. Such scanning is generally referred to as xe2x80x9cwafer mappingxe2x80x9d or xe2x80x9cmappingxe2x80x9d.
Sensors to carry out mapping have been incorporated into an end effector. U.S. Pat. No. 6,256,555, for example, describes an end effector with an integrated mapping capability. A fiber optic system is located at the tip of the end effector to provide a light path. The end effector tip is positioned proximal to the wafers, and then the end effector traverses up and/or down in front of the wafers to carry out mapping. Wafer location, presence, and orientation is determined by breaking of the light path. Another commercially available end effector includes a sensor, commercially available under the trademark xe2x80x9cHAMA,xe2x80x9d at the backside of the end effector to carry out mapping. This approach also allows horizontal wafers to be mapped by rotating the end effector around about a vertical axis so that the sensor faces the wafers to be mapped. In this position, the end effector traverses up and/or down in front of the wafers to carry out mapping.
Both of these conventional mapping approaches may be able to map horizontal wafers acceptably, but neither is able to map wafers in other orientations (e.g., vertical orientations) due to limitations of the sensor, limitations in the robot motion, limitations of the end effector motion, and/or limited volume within which the robot arm is allowed to move. It would be desirable to provide a system with mapping capability that can map wafers in a wide variety of orientations, e.g., horizontal and/or vertical, as desired.
Another aspect of various wafer handling devices is calibration or xe2x80x9cteachingxe2x80x9d a robot to move among and/or accurately position itself at a plurality of pre-selected positions. As mentioned above, in the fabrication of semiconductors, wafers are typically held in a wafer holding structure and then transferred to various pre-programmed processing locations by a robotic wafer handling system. In order to transfer such wafers, it is preferred that the robot have precise knowledge of spatial coordinates (e.g., x, y, z, r, xcex8, etc.) of a wafer at a variety of locations. A robot control system preferably provides the aforesaid knowledge to position the robot arm and end effector to releasably engage or disengage a wafer within a wafer holding structure.
After a tool is set up for the first time, serviced, upgraded, or modified, it is often desirable to teach, or re-teach as the case may be, the robot(s) in the tool the precise spatial coordinates as to location and dimensions of tool components to allow the robot to move rapidly among locales without collision.
Generally, such calibration or teaching involves using sensing mechanism(s) for the robot to sense spatial features of objects (e.g., wafer holding structures, tool boundaries, etc.) in its environment and establish spatial relationships between the robot and such objects. See, e.g., U.S. Pat. No. 5,822,498, which describes a manual method of calibration.
Calibration of a robot can occur not just manually with the help of an operator but also automatically by the robot itself. Manual calibration is less preferred due to time and safety concerns. Time requirements of manual calibration may be relatively high because an operator manually jogs the robot arm around to help determine spatial coordinates. Safety can be a concern for operators in manual calibration because of the force such robots can generate. In either case, teaching typically occurs with the help of sensing mechanism(s) on the robot and/or sensing mechanism(s) distributed around the robot""s operating environment. In some instances, sensing mechanism(s)s used to calibrate a robot have been integrated into robot end effectors. See, e.g., U.S. Pat. No. 6,075,335, which describes an automated approach for calibrating a robot. However, this and similar calibration methodologies do not rely solely or even primarily on an sensing mechanism(s) integrated within an end effector due to factors including limitations of the sensing mechanism(s), limitations in the robot motion, limitations in the end effector motion, and/or limited volume within which the robot arm is allowed to move. It would be desirable to provide robotic systems in which a robotic end effector includes a sensing mechanism(s) to carry out substantial aspects, if not the entirety, of an automated robot calibration methodology with enhanced motility in confined volumes.
The present invention relates to equipment and methods for manufacturing wafer or disk shaped materials, specifically including microelectronic devices, and specifically including semiconductor wafers. The invention specifically contemplates a robot system incorporating a versatile end effector that can be used to transport wafers, map wafers, and autocalibrate the movements of the robotic system. Typically, the end effector of the invention is rotatably and/or pivotably coupled to a robotic arm and includes an optical sensor system whose light path preferably includes a directional component that extends along a lengthwise axis of the end effector. Preferably, the end effector is independently moveable about at least two axes. These characteristics, singly or in combination, allow the end effector to carry out transport, mapping, and autocalibration functions within a relatively small volume and in a variety of orientations, including vertical and/or horizontal orientations and/or other desired orientations.
The end effector of the invention can be used for mapping wafers in a variety of orientations, including vertical and horizontal orientations, with efficiency of space. In general, the end effector can be used to map wafers in any orientation by positioning the end effector in an orientation so that its lengthwise edge incorporating the sensor system is proximal to the wafers and then moving the end effector through an axis that preferably is substantially perpendicular to the plane of the wafers so that the wafers can interrupt the light path.
The phrase xe2x80x9csubstantially perpendicularxe2x80x9d as used with respect to an end effector of the present invention moving in an axis relative to a plane of wafers so the wafers can interrupt the light path preferably means that an end effector of the present invention may traverse (i.e., map) a wafer(s) along one or more axes that form an angle with a main plane of the wafer(s) such that the end effector will not contact the wafer(s) during such traversing. In one preferred embodiment, such an axis may form an angle to a main plane of the wafer(s) of 90 degrees, optionally, plus or minus an angle in the range from 0 degrees to about 10 degrees, preferably in the range from 0 degrees to about 5 degrees, and more preferably in the range from 0 degrees to about 1 degree. During mapping, the main plane of the end effector may be disposed parallel or at an angle relative to the main plane of the items being mapped. Typically, the main plane of end effector 26 in the Figures is substantially parallel to the main plane of the items being mapped.
For example, the end effector can be used to map horizontal wafers by positioning the main plane of the end effector in a generally horizontal orientation so that its lengthwise edge incorporating the sensor system is proximal to the wafers. The end effector may then be moved along a linear, acruate, and/or other suitable axis that is substantially perpendicular to a main plane of the wafers so that the wafers can interrupt the light path. In another example, the end effector can be used to map vertical wafers by positioning the main plane of the end effector in a generally vertical orientation so that its lengthwise edge incorporating the sensor system is proximal to the wafers. The end effector may then be moved along a linear, arcuate, and/or other suitable axis that is substantially perpendicular to a main plane of the wafers so that the light path can be interrupted by the wafers. In this orientation for mapping vertical wafers, the end effector may be positioned above the vertical wafers in a reduced amount of headspace above the vertical wafers, e.g., a headspace having a height not much greater than the width of the inventive end effector.
Various exemplary embodiments of the present invention are described in the following specification and claims and drawings attached hereto.